Foamable polymer blend compositions

Abstract

Compatible blends of an ethylene/methacrylic or ethylene/acrylic acid dipolymer or a terpolymer with n-butyl or isobutyl acrylate with an ethylene/X/Y terpolymer, where X is vinyl acetate or an alkyl acrylate and Y is CO or SO2, with an elastomer, a blowing agent, and a curing agent can be readily formed into stiff foamed articles having very good physical properties, especially split tear and tensile strength. The foamed articles are useful, among others, in such applications as footwear, insulation, shock absorbance, floatation devices, seals and, gaskets.

I claim: 
     
       1. A compatible foamable, readily formable, curable polymer blend consisting essentially of the following components present in the following approximate weight amounts: (1) 50-100 parts of a dipolymer E/A or terpolymer E/A/B, wherein E is ethylene; A is acrylic or methacrylic acid; and B is n-butyl or isobutyl acrylate; the weight proportion of monomer A in both the dipolymer and the terpolymer being about 2-20% and the weight proportion of monomer B in the terpolymer being at most about 23%; the carboxylic acid groups in either type of polymer being either unneutralized or neutralized to an extent of at most about 71% with metal ions having a valency of from 1 to 3;     (2) 2-40 parts of a terpolymer E/X/Y, where E is ethylene; X is vinyl acetate or a C 1  -C 8  alkyl acrylate; and Y is CO or SO 2  ; the weight proportions of X and Y being as follows: Y about 1-15%;   X, when it is vinyl acetate, about 15-30%, and when it is an alkyl acrylate, about 10-55%;     (3) 2-40 parts of an elastomer;   (4) 1-10 parts of a blowing agent;   (5) 0-10 parts of an activator for the blowing agent;   (6) 0.5-10 parts of a curing agent for the E/X/Y terpolymer selected from peroxides, sulfur and sulfur-releasing agents, and diamines and their precursors;   (7) 0-15 parts of a processing aid; and   (8) 0-100 parts of a filler.   
     
     
       2. A blend of claim 1 wherein monomer A is methacrylic acid, and the weight proportion of methacrylic acid in the dipolymer or terpolymer (1) is 8-15%. 
     
     
       3. A blend of claim 2 wherein the neutralizing metal ions are selected from the group consisting of sodium, zinc, magnesium, and aluminum. 
     
     
       4. A blend of claim 1 wherein monomer B is n-butyl acrylate. 
     
     
       5. A blend of claim 1 wherein monomer B is isobutyl acrylate. 
     
     
       6. A blend of claim 1 wherein the amount of dipolymer or terpolymer (1) is 75-90 parts by weight. 
     
     
       7. A blend of claim 1 wherein monomer Y is carbon monoxide. 
     
     
       8. A blend of claim 7 wherein monomer X is vinyl acetate. 
     
     
       9. A blend of claim 8 wherein the amount of carbon monoxide in the terpolymer is at most about 7% by weight. 
     
     
       10. A blend of claim 7 wherein monomer X is an alkyl acrylate. 
     
     
       11. A blend of claim 10 wherein the alkyl acrylate is n-butyl acrylate, which is present in the terpolymer in an amount of about 15-35% by weight. 
     
     
       12. A blend of claim 1 which contains fillers. 
     
     
       13. A blend of claim 1 which contains processing aids. 
     
     
       14. A blend of claim 1 which contains a blowing agent activator in an amount of at least 0.5 part per 100 parts by weight of polymer blend. 
     
     
       15. A blend of claim 14 wherein the activator is zinc oxide or zinc stearate. 
     
     
       16. A blend of claim 1 wherein the elastomer is selected from the group consisting of natural rubber, polyisoprene, and polyurethanes. 
     
     
       17. A blend of claim 1 wherein the blowing agent is azodicarbonamide. 
     
     
       18. A blend of claim 1 wherein the curing agent is a peroxide.